Neutral particle beam devices presently under construction will be capable of producing hydrogen neutral beams having energies in the range of approximately 10 MeV and higher. Much more powerful beam devices are contemplated. If these devices are located in space they will be capable of delivering these beams to targets located at distances of many kilometers.
The aiming of charged particle beams has been well developed and used extensively in sending charged particle beams down long linear accelerators.
A technique involving laser resonance fluorescence has been proposed for sensing the direction of a neutral beam. See G. Rohringer, "Particle Beam Diagnostics by Resonant Scattering" (U), General Research Corp. Report No. CR-1-783(1977). In this technique the Doppler shift in laser induced fluorescence is measured to determine the angle between the fluorescence producing laser beam and the particle beam. This system is expensive and complicated, and requires that the beam energy and laser wavelength be known to a high accuracy.
Cross hairs have been used in ordinary telescopic rifle sights for aligning weapons for many years. The telescopic rifle sights work by aligning two sets of cross hairs optically with the intended target. The cross hairs have previously been aligned with the bore of the rifle, so that when the cross hairs are aligned the rifle is on target.